Method of firing furnaces



June 26, 1934. w TRlNKs 1,964,544

METHOD OF FIRING FURNACES Filed April 5, 1928 2 Sheets-Sheet l gwvemtozJune 26, 1934. w. TRINKS METHOD OF FIRING FURNACES 2 Sheets-Sheet 2Filed April 5. 1928 gwuwnto'o Ll/l Ill bO/d Trzn/(s 61 Momma PatentedJune 26, 1934 PATENT OFFICE METHOD OF FIRING FURNACES Willibald Trinks,Pittsburgh, Pa., assignor to Libbey-Owens-Ford Glass Company, Toledo,Ohio, a corporation of Ohio Application April 5, 1928, Serial No.267,726

'20 Claims. (01. 158-1175) This invention relates to furnaces and methodof firing the same.

One of the important objects of the invention is to provide a combustiontype furnace and '5 method of firing the same whereby a highly luminousand radiant flame is obtained.

Another object of the invention is to provide a furnace and method ofthe aforesaid character wherein the fuel is practically burned andconsumed before it leaves the furnace.

Still another object of the invention is to provide a furnace and methodof this nature where- -in the length as well as the direction of theflame may be adequately and efliciently controlled.

16 Still another object of the invention is to provide such a furnaceand method of firing the same wherein with the use of hydrocarbon fuelsmeans is provided for decomposing or cracking 2O velocity through aport, in proximity to or in the presence of a heating agent, forinstance, preheated air, also flowing at a low velocity, and thenaccelerating or facilitating complete combustion by introducing anelastic fluid by high velocity jets into the streams of slowly movingfuel and air near the mouth of the port.

Still another object of the invention is to provide a furnace and methodof this nature wherein the hydrocarbon fuel is first preheated to apoint just below its cracking temperature and then conducted to a portwhere it is subjected to heat above its cracking temperature to thusproduce an energetic breaking up of the fuel gas.

Various other objects, advantages and novel details of construction ofthis invention will be made more apparent as this description proceeds,especially when considered in connection with the accompanying drawings,wherein:

Fig. 1 is a fragmentary vertical longitudinal sectional view through aglass furnace constructed in accordance with this invention.

Fig. 2 is a fragmentary horizontal longitudinal sectional view takensubstantially on the plane.

indicated by line 2-'2 in Fig. 1.

Fig. 3 is a top plan view of the furnace.

Fig. 4 is a sectional elevational view of a reversing valve, and

Fig. 5 is a sectional View taken substantially on the plane indicated byline 5--5 in Fig. 4.

In glass melting furnaces and other combusemploy a. highly luminous andradiant flame. Likewise it is considered desirable and advantageoustopractically burn the fuel before it leaves the furnace and also tocontrol the length tion type furnaces it is generally expedient tov aswell as the direction of the flame produced. Hydrocarbons, such forinstance as tar, fuel oil, gasoline, acetylene and the like, which arerich in carbons, readily produce a flame of considerable luminosity.However, those hydrocarbons, such for instance .as methane or ethanewhich contains a considerable amount of hydrogen, have a tendency toproduce a clear, blue heat which can scarcely be called a flame. Iflight hydrocarbons of this character are to be burned to produce a flameit is necessary to crack them, that is, by heating them in the absenceof oxygen to break them up or decompose them into hydrogen and carbon.The extent of the decomposition is a function of the composition of thehydrocarbon, of the temperature to which it is heated and of the periodof time during which it is maintained at a high temperathe fuel byflowing the same slowly or at a low ture in the absence of oxygen. Forinstance, hydrocarbon containing a relatively small amount 7 of carbonmust be subjected to a higher temperature and maintained at thattemperature for a longer period of time before there is any perceptibledecomposition than a hydrocarbon containing a relatively greater amountof carbon.

In accordance with the present invention it is proposed to heat thehydrocarbon by the com-- bustion of a small portion of the fuel in aport of the furnace. This of itself, has been practiced before and isnot claimed as new. However, in accordance with this invention thedesired effect is obtained by admitting gas to the port of the furnaceat a low velocity and permitting it to flow towards the furnace under a0 layer or stratum of airalso flowing at a low velocity. Combustionoccurs at the boundary between the two fluids and the gas lying underthe flame of this combustion is heated and decomposed. The atoms ofcarbon thus formed coagulate and form flakes of soot.

The difficulty which has heretofore existed was not only that of burningthe hydrogen quickly enough to produce a brilliant or luminous flame butalso to burn the flakes of soot before they leave the furnace. Theslower the flow of gas and of air, the greater is the breaking-up effectbut at the same time the combustion is slower and less perfect. As amatter of fact the two actions, that is, breaking up and completecombustion are contrary and incompatible. While attempts have been madeto obtain proper mixing by the shape of the port such attempts havegenerally been only partly successful beno cause they diminish one ofthe above actions by favoring the other.

In accordance with the present invention I propose first cracking thegas as above described and then introducing an elastic fluid by highvelocity jets into the port near the mouth of the latter, the velocityof the jets being sufficient to produce a turbulent mixing and quickcombustion. An elastic fluid such as compressed air can be used but Iprefer to use gas as a mixing medium because it has no tendency toreduce flame temperature.

By reference to the drawings and in particular to Figs. 1 and 2 thereofone manner of carrying the present invention into execution will bedescribed in detail.

In the drawings the reference character 10 indicates a heating devicesuch as a regenerator connected at its upper end by means of a duct 11to the furnace port 12. Preheated air is supplied by the regenerator 10and passes through duct 11 to the port 12 and over bridge wall 13 and byreason of its buoyancy and its inertia it has a tendency to hug the roofor top portion 14 of the port. Viscous drag induces a secondarycirculation in the otherwise dead space indicated by the referencecharacter 15, somewhat in the manner indicated by the arrows 16. Thiscirculation carries a small portion of the fuel gas which is admittedthrough fuel supply pipes 17 communicating with the port 12 at eitherside thereof. Extending longitudinally of the port and arranged betweenthe fuel pipes 1'7 is a partition or monkey wall 18. g

The fuel supply pipes 1'7 are purposely of rather large diameter so thatthe fuel will not be forcibly ejected therefrom to thus prevent the samefrom. impinging against the wall 18. If the fuel did impinge againstthis wall it would probably spread into jets and flow into the airstream. On the contrary with the herein shown and described arrangementthe greatest portion of the fuel introduced through the fuel pipes 17,because of the slight pressure produced by the incoming gas in the deadspace 15, follows substantially the course or path indicated by arrow19. While the gas is flowing through the port toward the outlet end ormouth 20 thereof the preheated air is likewise flowing therethroughtoward the mouth 20, the preheated air clinging close to the roof 14 ofthe port while the gas flows in a substantially separate stream beneaththe stream of air. At the boundary between the air and fuel gas anirregular fluttering combustion occurs in which only a small fraction ofthe air and fuel gas partake. The heat from this combustion, togetherwith the heat coming from the walls of the port cracks or decomposes h hdrocarbons. t rist experience has shown that the stratificaton of fueland air persists in the furnace and that combustion is extremely slow,in fact too slow for useful purposes, unless a thorough mixing takesplace at the mouth of the port. In accordance with my invention Ipropose to obtain this mixing by injecting a small amount of an elasticfluid such as fuel gas or air through. pipes 21 and nozzles 22. The jetsof fuel gas or other fluid, under a pressure of, for instance one toflve pounds per square inch, is sufllcient to produce an excellentturbulence and mixing. In practice I have found that if fuel gas isinjected, about fifteen per cent of the total fuel gas used should passthrough the nozzles 22. However, obviously the percentage of gasentering the port through the nozzles 22 may be decreased or increasedas found desirable, necessary or expedient. While as mentionedcompressed air may be ejected through the nozzles 22 with the samemixing effect as fuel gas nevertheless compressed air results'in aslight lowering of the flame temperature and consequently is not aseilicient as fuel gas in this respect.

In order to'control the length and direction of the flame produced, thepipes 21 are preferably adjustably mounted by means (not shown) so thatthey may be swung in a horizontal plane or in a vertical plane assuggested by dot and dash lines in Figs. 1 and 2. If the pipes 21 areswung to the dot and dash position 21a (see Fig. 2) mixing occurs morerapidly. The ports are burned out at points just within the mouththereof. If, on theother hand, the pipes 21 are moved to the positionindicated by dot and dash lines 21b mixing occurs less'rapidly.Obviously the most satisfactory and efiicient adjustment for the pipes21 may be determined upon full consideration of the conditions inexistence and depends upon the length of the furnace, the direction offlame travel, composition of fuel, etc.

If, as shown in Fig. 1, the pipes 21 are adjusted to the position 210indicated by dot and dash lines then the flame is shot down onto or inthe direction of the'glass bath 23. ,On the other hand, if the pipes 21are adjusted to the position 2112 indicated by dot and dash lines inFig. 1 the flame is lifted. In glass furnaces such control is of extremeimportance because it is frequently necessary to direct the flame closeto the bath and yet not sufliciently close thereto to burn away certainfluxes and spoil the glass. It is also important that the pressure inpipes 21 be sumciently great to produce the momentum which is necessaryto drag gas, air and the products of combustion into the wake of thejets. The lower the pressure in the pipes 21 the larger they must be andthe more fluid must be passed through them in order to bring about thisdesirable condition and the greater is the fraction of uncracked fuelgas.

If the fuel gas is extremely lean, containing only methane, or evenconsisting of hydrogen with only a small admixture of hydrocarbons, itbecomes necessary to preheat the fuel gas before it enters pipes 14 and21. To this end independently flred heaters may be employed forthispreheating and the present invention contemplates the use of suchheaters, although their use is not always necessary. However anyexternal preheating of the fuel is not carried far enough to produce anenergetic breaking-up of the fuel gas but yet far enough to cause anincipient breakingup, the final breaking-up and coagulation of thecarbon atoms into soot flakes occuring in the port.

By reference particularly to Fig. 3 a method and means will be describedwherein the waste heat of the furnace may be utilized for preheating thefuel gas. In this figure a conventional type of furnace is shown ascomprising a glass containing receptacle 24 connected by ports 25 withthe regenerators 10. The reference character 26 indicates a main fuelsupply line which divides into two branch lines 27, these branch linesextending through the tunnels 28' of the regenerators 10. These branchlines are connected to a reversing valve 29 (see particularly Figures 4and 5). Also connected to the reversing valve 29 are conduits 30 whichact in the nature .one or the other of the conduits of headers to supplyfuel to the plurality of fuel supply pipes 17. The reversing valve 29 isprovided with a valve member 31 by means of which 30 may be put underpressure at one time, depending upon the direction of flame travel.

The tunnels under the regenerators are particularly well adapted forpreheating the fuel gas because the temperature in them is notsumciently high to crack the fuel gas, which action would cause thepipes to clog with soot. At the same time the temperature is sufdcientlyhigh to require only a slight additional supply of heat for the purposeof starting the cracking operation as the fuel is introduced into theports.

While an embodiment-of the invention has been described herein somewhatin detail it will be readily apparent to those skilled in this art thatvarious modifications, rearrangements and changes may be resorted towithout departing from the spiritand scope of this invention and to thisend reservation is made to make such changes as may come within thepurview of the accompanying claims.

I claim:

1. In the method of firing furnaces,. those steps which consist inflowing a hydrocarbon fuel andair in substantially separate butcontacting streams at a low velocity through a furnace port so thatthere is no material intermingling thereof, and in then thoroughlymixing, these streams adjacent the mouth of the port by high velocityjets of an elastic fluid.

2. In the method of firing furnaces, those steps which consist inflowing a hydrocarbon fuel and preheated air in substantially separatebut contacting streams at a low velocity through a furnace port so thatthere is no material intermingling thereof, causing the preheated air tocrack or decompose the hydrocarbons while travcling at such lowvelocity, and in then thoroughly mixing these streams at the mouth ofthe port by high velocity jets of an elastic fluid.

3. In the method of firing furnaces, those steps which consist inflowing a hydrocarbon fuel and air in substantially separate butcontacting streams at a low velocity through a furnace port so thatthere is'no material intermingling thereof, and in then thoroughlymixing these streams adjacent the mouth of the port by high velocityjets of fuel. s

4. In the method of firing furnaces, those steps which consist inpassing a hydrocarbon fuel and air in substantially separatesuperimposed streams without a dividing wall through a furnace port at alow velocity so that there is no material intermingling thereof,. and inthen thoroughly mixing these streams near the mouth of the port by highvelocity jets of an elastic 5. In the method of firing furnaces, thosesteps which consist in passing hydrbcarbon fuel and preheated air insubstantially separate superimposed but contacting streams through afurnace port at a low velocity so that there is no materialintermingling thereof, causing the preheated air to crack or decomposethe hydrocar-- bons while traveling at such low velocity, and in thenthoroughly mixing these streams near the mouth of the port by highvelocity jets of an elastic fluid.

6. In the method of firing furnaces, those steps which consist inflowing a hydrocarbon fuel at low velocity through a furnace port,heating the fuel partially by the heat of combustion of a which consistin fuel at low velocity through a furnace port, si-

combustion of a, fraction fraction thereof and-injecting additional fuelat high velocity near the mouth of the port.

7. In the method of firingfurnaces, those steps which consist in flowinga hydrocarbon fuel at low velocitythrough a furnace port, heating thefuel partially by the heat of combustion of a fraction thereof andinjecting additional fuel at high velocity adjacent the mouth of theport through one or more nozzles in the direction of the desired flametravel.

' 8. In the method of firing furnaces, those steps which consist inflowing a stream of hydrocarbon fuel at low velocity through a furnaceport, simultaneously flowing a stream of air at low velocity throughsaid port, maintaining the stream of air'substantially separate from butin contact with the stream of hydrocarbon fuel so that there willbe nomaterial intermingling thereof, heating the fuel by radiation from thefurnace and port walls and also by the heat of combustion of a fractionof the fuel, and mixing the streams of fuel and air near the mouth ofthe port by high velocity jets of an elastic fluid.

9.- In the method of firing furnaces, those steps flowing a stream ofhydrocarbon multaneously flowing a stream of preheated air at lowvelocity through said port, maintaining the stream of air substantiallyseparate from but in contact with the stream of hydrocarbon fuel so thatthere will be no material intermingling thereof, heating the fuel byradiation from the furnace and port walls and also by the heat of of thefuel, and mixing the streams of fuel and air adjacent the mouth of theport by high velocity jets of relatively small proportions of fuel. I

10. In the method of firing furnaces, those steps which consist inflowing a stream of hydrocarbon fuel at relatively low velocity througha furnace port, flowing a stream of preheated air at a relatively lowvelocity through said port, in maintaining the streams substantiallyseparate but in contact with one another so that there will be nomaterial intermingling thereof, in causing combustion to occur at theboundary between said air and fuel in which only a small fraction of theair and fuel partake but which is suflicient to cause cracking of thehydrocarbons, and in then effecting a positive and turbulent mixing ofthe streams of air and fuel adjacent the mouth of the port to acceleratecomplete combustion.

11. In the method of firing furnaces, those steps which consist inflowing a stream of hydrocarbon fuel at a relatively low velocitythrough a furnace port and simultaneously flowing a preheatedv stream ofair also at a low velocity through said port, in maintaining the streamssubstantially separate but in contact with one another so that therewill be no material intermingling thereof,

in causing combustion to occur at the boundary between theair and fuel,and mixing the streams of fuel and air by high velocity jets of anelastic fluid adjacent the mouth of the port.

12. In the method of firing furnaces, those steps which consist inflowing a stream of hydrocarbon fuel through a furnace port at lowvelocity and heating the same, flowing preheated air through said portin a substantially separate stream and mixing the streams of fuel andair by high velocity jets of an elastic fluid adjacent the mouth of theport.

13. In the method of firing furnaces, those steps which consist inpreheating a hydrocarbon fuel to a. point just below its crackingtempera.-

ture, flowing said fuel through a furnace port and heating it above itscracking temperature and mixing said fuel and air adjacent the mouth ofthe port by high velocity jets of an elastic fluid.

14. In the method of firing furnaces, those steps which consist inpreheating a hydrocarbon fuel to a point slightly below its crackingtemperature, flowing said fuel through a furnace port and heating it toa point above its cracking temperature by the combustion of a smallfraction thereof and mixing said fuel and air adjacent the mouth of theport by jets or high velocity.

15. In the method of firing furnaces, those steps which com ist inpreheating a hydrocarbon fuel to a point ust below its crackingtemperature, flowing the same at a low velocity through a furnace port,flowing a stream of preheatedv air simultaneously through said port,heating the fuel in the port to a point above its cracking temperatureby the combustion of a small fraction of the fuel and air at theboundary therebetween.

16. In the method of firing furnaces, those steps which consist inpreheating a hydrocarbon fuel to a point just below its crackingtemperature, flowing the same at a low velocity through a furnace port,flowing a stream of preheated air simultaneously through said port,heating the fuel in the port to a point above its cracking temperatureby the combustion of a small fraction of the fuel and air at theboundary therebetween and mixing these streams at the mouth of the portI by high velocity jets of an elastic fluid.

17. In the method of firing furnaces, those steps which consist inflowing hydrocarbon fuel and air in substantially separate superposedbut contacting streams at a low velocity through a furnace port so thatthere is no material intermingling of the two streams, causing a partialcombustion to occur at the boundary between the streams of air and fuelin which only a small fraction of the air and fuel partake but which issufficient to effect cracking of the hydrocarbons, flowing the streamsat low velocity to the mouth of the port, and in then injecting into thestreams high velocity jets of an elastic fluid to thoroughly mix thesame and effect complete combustion.

18. In the method of firing furnaces, those steps which consist inflowing hydrocarbon fuel and air in substantially separate superposedbut contacting streams at a low velocity through a furnace port so thatthere is no material intermingling of the two streams; causing a partialcombustion to occur at the boundary between the streams of air and fuelin which only a small fraction of the air and fuel partake but which issufficient to effect cracking of the hydrocarbons, flowing the streamsat low velocity to the mouth of the port, in then injecting into thestreams high velocity jets of an elastic fluid to thoroughly mix thesame and effect complete combustion, and in controlling the length anddirection of the flame produced by varying the angle of injection of thehigh velocity jets of elastic fluid into the said streams.

19. In the method of firing glass melting furnaces, those steps whichconsist in flowing a hydrocarbon fuel and air in substantially separatebut contacting streams at a low velocity through a furnace port for asubstantial distance sufficient to effect the cracking of thehydrocarbons without causing any material intermingling of the fuel andair, and in then thoroughly mixing these streams adjacent the mouth ofthe port by high velocity jets of an elastic fluid.

20. In the method of firing glass melting furnaces, those steps whichconsist in flowing a hydrocarbon fuel and preheated air in substantiallyseparate superimposed contacting streams at a low velocity through afurnace port for a substantial distance sufficient to effect thecracking of the hydrocarbons without causing any material interminglingof the fuel and preheated air, and in then thoroughly mixing thesestreams adjacent the mouth of the port by high velocity jets of fuel.

WIILIBALD 'I'RINKS.

